Issues with new heating zone

powerade

John, thank you so much for doing that. It was very kind. I must confess that I think I am starting to lose the plot with this. Earlier today I put a temperature and humidity gauge from a weather station pack on top of the manual dial thermostat in Zone 2 to see if it recorded the same room temperature as the digital thermostst. There was only .2 of a degree in it so I was, therefore, comfortable with the accuracy of the digital thermostat.The broadband went down around 5, at which point Zone 2 was 22.2 degrees and it came back on at 7:15. At 9pm Zone 2 was displaying a temperature of 22 but the weather station was displaying 21.4 degrees. Zone 2 had definitely cooled down so I did not trust the reading on the digital thermostat. I reset the temperature using the Amber App to 23.5 and both the digital stat and weather station temperatures increased by the same amount in the last hour. Which starting point do I believe, however? On top of that the boiler cycled with both zones on and I have never seen that before. What on earth is going on .......

John.G

I'm afraid I don't know, you may see some difference now if/when you open all the lock shields & TRVs in zone 2, you can then just use the room stat(s) to control the temperature and see how you get on, don't know what the state of play with zone 1 is, if its heating up OK maybe leave well enough alone. If the boiler doesn,t cycle with both zones on then, apart from your own observations re heat up times, this would indicate that zone 2 is now outputting to its full capacity.
You might also just sit back and let the system run away for a few days and just use the roomstats in both zones to control the house temperature, after all, that's what they are for. I am not a big fan of using roomstats & TRVs in the one zone even though I suppose there is some logic/merit in it.

K.Flyer

powerade wrote: »

Can I just ask a quick question regarding the lockshield valves. When the heating was split into two zones, the plumber replaced all of the TRV's and the lockshield valves. I tried to turn a couple of then in Zone 2 and they were extremely difficult to turn in either direction. I did manage to open two of them by approx one turn and, almost immediately, I could feel a difference in the radiator temperature. Is there any harm in opening them any further?

Open all of them fully for now, and starting from cold, compare how each of them heat up when you turn on zone 2 heating only.
At the same time checking the pipe from the by-pass valve to see if it is getting as hot as usual.

powerade

By way of background, Zone 2 is a self contained appartment which I rent through AIRBNB plus one bedroom in my living area. My current guest messaged me this evening to say that she was cold but I was seeing a thermostat temperature of 22 degrees. So, I have to get on top if this.

K.Flyer

Everyone has their own definition of cold.
I've met people who would be using the heating almost all year round, they just prefer higher temperatures indoors.

John.G

K.Flyer wrote: »

Open all of them fully for now, and starting from cold, compare how each of them heat up when you turn on zone 2 heating only.
At the same time checking the pipe from the by-pass valve to see if it is getting as hot as usual.

The pump on this boiler is set at 3M constant pressure so there should be a relatively constant by pass of ~ 5 LPM if the ABV is set to say 0.25, which theoretically added to the zone flowrate shouldn't affect the temperature rise through the boiler for any given heat input but in practice due to pipe friction losses the actual radiator flowrate will tend to fall and because of the ongoing problems with zone 2 rad output and boiler cycling it may be better to ensure that there is no by pass and get as big as possible a flow through the rads.

powerade

K.Flyer wrote: »

Everyone has their own definition of cold.
I've met people who would be using the heating almost all year round, they just prefer higher temperatures indoors.

Yes, that is very true and sometimes I think that people assume that the place is cold just because the radiators are cold.

K.Flyer

John.G wrote: »

The pump on this boiler is set at 3M constant pressure so there should be a relatively constant by pass of ~ 5 LPM if the ABV is set to say 0.25, which theoretically added to the zone flowrate shouldn't affect the temperature rise through the boiler for any given heat input but in practice due to pipe friction losses the actual radiator flowrate will tend to fall and because of the ongoing problems with zone 2 rad output and boiler cycling it may be better to ensure that there is no by pass and get as big as possible a flow through the rads.

Which is why I suggested opening all off the lock shield valves fully and start from there.
If the zone is plumbed and balanced correctly then the bypass should remain closed during normal operation.

powerade

I have just closed and reopened the lock shield valves by three turns. The valve on the towel rail felt fully open after three turns the the valves on all of the other radiators felt like they could turn quite a bit further. Should I keep turning them or leave them as is? Also, I have the ABV fully closed. Is that right?

K.Flyer

powerade wrote: »

I have just closed and reopened the lock shield valves by three turns. The valve on the towel rail felt fully open after three turns the the valves on all of the other radiators felt like they could turn quite a bit further. Should I keep turning them or leave them as is? Also, I have the ABV fully closed. Is that right?

Open them all fully, it's the only place to start.
The towel rail can be left approx midway open.
Check from a cold start if all the radiators heat up fully at the approximately the same time and how quickly and see how it all interacts with the zone stat and your boiler.

John.G

powerade wrote: »

I have just closed and reopened the lock shield valves by three turns. The valve on the towel rail felt fully open after three turns the the valves on all of the other radiators felt like they could turn quite a bit further. Should I keep turning them or leave them as is? Also, I have the ABV fully closed. Is that right?

Some of these lock shield valves have a plastic "knob" that you can keep turning in both direction until the cows come home and nothing happens, you may see a little securing screw on the top or there may be nothing, just remove the screw and/or pull the knob straight up to reveal the valve spindle, then you can turn this with your adjustable spanner or whatever but just be satisfied that they are all fully opened IE ANTICLOCKWISE by ~ 3 turns when finished.

Just saw K.Flyer's post there now.

And, yes, leave the ABV closed for now.

powerade

I am still testing zone 2 but all of my testing still shows the same dramatic difference in the rate of temperature increase between Zones 1 & 2. The digital thermostat rooms in each zone are roughly the same size, they both have two external walls, the radiators are the exact same size, the windows are triple glazed and the radiators both get scalding hot. The main differences between the two control rooms are as follows:
1. The external walls in Zone 2 are insulated with 82mm warm boards and 80% of the internal stud partitions have between 50 to 100mm of soundproofing /heat insulation. So, it is very tightly sealed. Zone 1 external walls have plasterboard with about 20mm insulation and the internal partitions have no insulation. There is also an open fireplace with an inset electric fire (not used). Zone 1 in comparison to Zone 2 is draughty.
2. Zone 1 has 11 mm underlay and carpet. Zone 2 has 5mm underlay and 12mm laminate flooring
3. The rate of heat loss in Zone 2 is significantly slower than Zone 1 which is, presumably, down to the insulation.

What I am wondering is whether the convection of heat in Zone 2 is slower than Zone 1 because of the difference in air tightness of the two zones. Hence the reason why the temperature is so slow to rise and why the flow temperature when Zone 2 is running on its own rises above the set point very quickly and the boiler cycles very frequently.

Does that make any sense at all?

John.G

Can't comment on the insulation except to observe that Zone 1 is carpeted and Zone 2 is not.

You also state:
3. "The rate of heat loss in Zone 2 is significantly slower than Zone 1 which is, presumably, down to the insulation."
wouldn't this mean that it should heat up faster as well??

Can you just measure even roughly the dimensions of each room in zone 2 and the dimensions of each rad and whether a single/double rad.

Also, are all the rads piped on their bottom ends ie none are piped in the bottom and out the top or vica versa.

Can you measure the temperature in each zone 2 room with your heat scanner and see how they compare with the roomstat temperature.

Are all the rads now in zone 2 roasting hot to the touch, all over.?

What is the boiler output set to and is the flow temperature still changing "widely" while cycling?.

powerade

I opened all of the lock shields fully on the radiators in Zone 2 and ran both zones separately for 70 minutes. In 48 minutes Zone 1 increased by 3 2 degrees compared with 1.6 degrees in Zone 2. After 70 minutes Zone 1 increased by 4.7 degrees compared with 2.2 in Zone 2.
I had thermostats in each of the three rooms in Zone 2 (I excluded the en-suite) and the rate of temperature increase was the exact same in all of them.
I also compared the rate of temperature increase in Zone 1 in the two main rooms which both have similar characteristics and there was only .2 of a degree in it.
Zone 1 did not cycle in the 70 minutes but the flow temperature was up to 67 degrees so it was building up to it. Zone 2 cycled twice in 70 minutes with two consecutive 204's followed by a 202.
The radiators are not undersized John but I will post the room dimensions and radiator sizes later.
So, nothing has changed in relation to the rate of temperature increase issue even though I think that the radiators are getting warmer in Zone 2. So, that takes me back to the main difference between Zone 1 and Zone 2 and it is insulation. I totally agree John that I would expect the temperature to rise more quickly in a well insulated room compared to a poorly insulated one but that is not what I am experiencing. In these relatively air tight rooms which are slow to lose heat, there must be reduced air circulation and, consequently, convection of heat. For example, if I turn Zone 1on and I go into my poorly insulated living room, I can feel the heat as soon as I open the door after a very short time. That is not the case with any of the rooms in Zone 2. I am back talking to Worcester Bosch about this just to be absolutely sure that the boiler is behaving as expected.

John.G

The radiator dimensions will give a good clue,
What is the max output setting of the boiler just now??>

powerade

24 KW

K.Flyer

John.G wrote: »

The radiator dimensions will give a good clue,
What is the max output setting of the boiler just now??>

I was thinking that as well. Rads may be undersized.

Wearb

K.Flyer wrote: »

I was thinking that as well. Rads may be undersized.

Or in a kind of dead zone. A measure of the return and flow temps. at the rads would also let you know how well the rad is dissipating the heat. With "modern" rads convection plays a big part in heat transfer. Blocking the flow at the bottom of the rad can slow down the convection rate.

John.G

The boiler return flow temp if available would tell a lot, we have the pump curve(s) so it would be very easy to calculate the flowrate through the 4 rads and because Powerade stated a number of times that he had no problem with zone 2 heat up prior to zoning then any flow restriction should be apparent once the rad dimensions are known. All we know for certain is that the combined output of zone 2 rads is < ~ 6 kw at the moment as the boiler starts cycling.

powerade

There is nothing in front of any of the radiators in Zone 1. Is there a benchmark temperature difference between the flow and return? I have seen a number of posts that suggest that the return temperature should be a maximum of 55 degrees C for the boiler to condense.
So, on to room sizes and rads.
1. Living room/kitchen: 20.21 sq metres. Rad is a double with grille, 140 x 50. South facing. This is where the digital thermostat is located.
2. Bedroom: 11.23 sq metres. Rad is a single with grille, 180 x 50. North facing
3. Bedroom: 12.6 sq metres. Rad is a single with grille, 140 x 60. North Facing
4. En suite 2 5 sq metres. Towel rail is 50 x 110. West facing.
This evening I am only running Zone 1. I noticed earlier that the temperature was starting to rise at 67 degrees. I turned the bedroom radiator TRV back up to 5 (had lowered it to 2) and moved the radiator cover away from the radiator in the hall. After about 30 seconds the temperature fell back to 65 degrees and it has been happily putting along at that level for the last hour. That proves that Zone 1, at the maximum radiator output ,must be pretty close to 7kw so Zone 2 must be significantly lower, given that it is much smaller and most of the Rads are singles.
The pipes are all connected to the bottom of the radiators and the ceilings are standard height, 2.4m.

powerade

I note that you mentioned the behaviour of Zone 2 prior to the zoning work John and that has been troubling me as it doesn't make sense in the context of what is happening now. However, I think I can make sense if it now.
Prior to the two zones being created, when the heating was on it was on in the entire house with some TRVs lowered. Typically during the day I would run it at 18 degrees and in the evening 23 degrees. Given that the rate of heat loss is very slow in Zone 2, the temperature would always have been warmer in Zone 2 compared to Zone 1 as it was only really off overnight. So, in the morning Zone 1 might need to rise by 5 degrees to get to the set temperature of 18 but the starting temperature for Zone 2 would probably be at least 18 degrees so it would probably have gone up to say 19.5 degrees by the time that Zone 1 reached temperature. Every time that Zone 1 topped up (max permitted temperature drop is .2 of a degree), at some point Zone 2 would start to go up because Zone 1 was losing heat much faster than Zone 2. Then when the evening came and Zone 2 was already roasting but Zone 1 had to rise from 18 to 23 degrees, that would probably have added a further 2 degrees to the temperature in Zone 2. I used the weather station to keep an eye on Zone 2 and there were evenings when I could see that the temperature was at 25/26 degrees.It didn't help, of course, if people were cooking in Zone 2.

John.G

powerade wrote: »

There is nothing in front of any of the radiators in Zone 1. Is there a benchmark temperature difference between the flow and return? I have seen a number of posts that suggest that the return temperature should be a maximum of 55 degrees C for the boiler to condense.
So, on to room sizes and rads.
1. Living room/kitchen: 20.21 sq metres. Rad is a double with grille, 140 x 50. South facing. This is where the digital thermostat is located.
2. Bedroom: 11.23 sq metres. Rad is a single with grille, 180 x 50. North facing
3. Bedroom: 12.6 sq metres. Rad is a single with grille, 140 x 60. North Facing
4. En suite 2 5 sq metres. Towel rail is 50 x 110. West facing.
This evening I am only running Zone 1. I noticed earlier that the temperature was starting to rise at 67 degrees. I turned the bedroom radiator TRV back up to 5 (had lowered it to 2) and moved the radiator cover away from the radiator in the hall. After about 30 seconds the temperature fell back to 65 degrees and it has been happily putting along at that level for the last hour. That proves that Zone 1, at the maximum radiator output ,must be pretty close to 7kw so Zone 2 must be significantly lower, given that it is much smaller and most of the Rads are singles.
The pipes are all connected to the bottom of the radiators and the ceilings are standard height, 2.4m.

Condensing will only be starting at a return temp of 55C, see chart, I would think that the vast majority of condensing boilers are rarely if ever in condensing mode but that's another discussion.

Re Zone 2 rads (see file) I reckon the total output of the rads is ~ 5.8 kw "50deg" rad but assuming a 10 deg deltaT between flow/return then the total output is ~ 4.8 kw "43 deg" rad and that is borne out by the boiler cycling.

L/room rated o/put 2018W actual o/put 1654W Area 20.21M2 w/M2 82
Bed 1 rated o/put 1512W actual o/put 1239W Area 11.23M2 w/M2 110
Bed 2 rated o/put 1371W actual o/put 1124W Area 12.60M2 w/M2 89
e suite rated o/put 924W actual o/put 758W Area 2.5 M2 w/M2 303

Total rated output 5825W Total actual o/put 4775W Average W/M2 146

I would think that in a well insulated house that anything > 80W/M2 should give adequate heating up time but others on here will have a better idea I would think.

powerade

The en-suite is 2.5sq metres. So the radiator sizes are ok? I guess that the next step is to measure the flow and return temperatures from each of the rads. Thank you for taking the time to work out the calculations.

John.G

Yes, they seem OK to me anyhow, if you can get a reasonably accurate measurement between the flow/return then that would be good also,

One other thing you might do sometime after zone 2 has fully heated up is to (temporarily) reduce the boiler max output (input) to its minimum of 7kw and watch a few more cycling anti-cycling modes, you should also get status 200 (CH system being heated) apart from status 204 (system waiting) and status 202 (anti rapid cycling), also note down the minimum flow temperature during this period. You will then have a bit of ammo when you talk (or your plumber) to WB, unfortunately, all available info seems to indicate that WB will tell you that the boiler should not cycle, you are lucky in one sense that you have a combi because if you were trying to heat up a hot water cylinder only during the summer where the coil demand (when hot water cylinder nears its set point) will be lower than the boiler minimum output then you could be in trouble based on this boiler's antics.

powerade

After each 204 status I get a 283 and then a 284 status for a nano second, then 200 as the temperature shoots up to 70/71 degrees and then either another 204 or a 202. If I allow Zone 2 to fully heat up John, I don't think that it will 204 or 202 when it is just topping up. Should I try it from initial start up perhaps as I will know pretty quickly what the impact is. I contacted Biworld yesterday regarding the ABV but I am finding it difficult to get a simple answer. They appear to be saying that water will always flow through the valve and the horizontal bypass pipe. The role of the valve is to stop water entering the flow pipe when the flow pressure reaches a certain point (driven by the closure of TRVs). Does that mean that a certain amount of water is being pumped straight back to the boiler without going near the radiators? WB have confirmed that I do need the ABV so I have no idea what purpose the internal one serves. Would anyone know where I can buy a set of pipe clamp thermometers? I rang a number of plumbing suppliers and drew a complete blank.

John.G

No, just do it the way I suggested because it should take ~ 4/5 minutes to raise the temperature from 70C to 75C if outputting ~ 6kw. If its still overshooting and cycling at this minimum setting then it suggests to me that its initial firing setting is quite high (despite its 6 kw output) and it just can't or isn't ramping down in time before it hits 75C.

ABV
The role of the ABV ideally should serve two purposes, (1) to maintain a minimum flow through the boiler by diverting some of the water from the flow into the return and hence through the boiler. (2) To remove residual heat from the boiler when all zone valves close but to achieve this then the boiler controls must/should incorporate a pump overrun to delay the pump from stopping for a predetermined time.
Now because WB have set up the pump control in constant pressure mode (@3m head) then the ABV has to pass a certain amount of water at all times so the ABV should (maybe) be set at index ~~ 0.25, you might ask Biworld for a capacity chart, but 0.25 shouldn'e be a bad starting point.
You might also ask WB if the boiler requires cooling down after all zone valves close does the boiler actually have a pump overrun and if not how is the residual heat removed?. IF they say that the residual heat does not have be removed then OK but it will certainly impact the anti rapid cycling. (the Vokera Vision 20S does have pump overrun)

powerade

Three hours and 20 minutes today to get Zone 2 from 11.8 to 18 degrees. I was in Zone 2 for most of the afternoon and i didn't notice any significant change in the radiator temperarure. It was lovely and warm in close proximity to the radiators but not very warm as I moved away from them. I changed the maximum output earlier to 7kw and did not notice any change in the cycling pattern. I did notice, however, that the boiler pressure increased which I didn't like. I also realised today that there appears to be an expansion vessel fitted in the attic (photos attached) and I don't know if that might have any impact on these heating issues. I now have to find a practical way to work with Zone 2 and I think that I will have to leave it on continuously when I have guests and possibly run it at 18 degrees overnight. I think that the configuration of my system can be tweaked to reduce the level of cycling but I don't think that will resolve the issue with the rate of temperature change in Zone 2 versus Zone 1. I have to get the flow and return temperatures and that takes me back to my earlier question, any advice on where I can buy a set of pipe clamp thermometers? I had already asked WB about the expected boiler behaviour when the zone valves close but I have not heard back from them yet.
On a positive note, the rate of temperature increase has improved in Zone 2 which I think is down to adjusting the lockshields and the frequency of short cycling has reduced. I think that is mainly attributable to removing the TRV head from the radiator in the living room in Zone 2 (but I could be wrong).

John.G

I don't think the extra E.vessel will do any harm.

Did you observe the flow/return fluctuations when cycling and was the anti rapid cycling still coming in a 7 kw output?. As long as the boiler pressure didn't rise > 2.2 bar I wouldn't worry.

Here is a link to a RS thermometer supplied with, I think two "bead" sensors, you can ring RS and enquire. https://ie.rs-online.com/web/p/digital-thermometers/1231937/

powerade

I learnt something new from WB today. Apparently a 204 and a 202 are one and the same thing! When the flow temperature rises 6 degrees above the set temperature, the boiler will kick off a anti rapid cycle. When it starts it will have a 204 status and if the desired temperature us achieved in less than the programmed rapid anti cycle time (3 minutes in my case), the status will change to 202 until the full anti cycle has completed. The burner will then fire, the status will change to 200 and, If the flow temperature has not cooled off sufficiently it will kick off another rapid anti cycle. So, you cannot have a 204 without a 202 unless the required temperature is achieved in the exact programmed anti cycle time. So, to answer your question, the boiler cycled exactly as before with the max output set at 7KW, I.e. 2 204's and one 202. You will never see the temperature displayed below 61 degrees in a 204. When it gets to a 202, the starting point will usually be 59 degrees. The level of subsequent drop will depend on the length of time that the rapid anti cycle has left to run. At a setting of 7KW it was settling at 57/58 degrees which is no different to what I have seen at a setting of 24KW. The flow temperature is still set at 65 degrees btw.
WRT the flow temperature, in my head it's like turning on a hot tap. It takes a while to get to the set temperature but once it's there, it stays there. However, that's not the way that it appears to work in practice. If I turn off Zone 1, the flow temperature displayed will rise, typically to 71 degrees and it will stay at 71 degrees for some time. If I immediately turn on Zone 2 (from cold) the boiler will immediately go into a 204 and then a 202. The temperature will plummet and today it dropped to 20 degrees before the burner fired. Why is that? It must have something to do with the fact that the water in the pipes in Zone 2 is cold but, if I go back to my hot tap analogy, to my mind the hot tap was turned off for a second and then turned back on so I wouldn't expect the water to be cold. I have seen these extreme temperature drops befioe but I don't think that it was a Zone 1 to Zone 2 switch that triggered them.
Thank you for the link.

John.G

Very in interesting, no major problems in cycling in first instance(s) as the variation is ~ 7/8C perfectly acceptable IMO.

Its the second part I'm having a bit of difficulty understanding...……

"If I turn off Zone 1, the flow temperature displayed will rise, typically to 71 degrees and it will stay at 71 degrees for some time. If I immediately turn on Zone 2 (from cold) the boiler will immediately go into a 204 and then a 202. The temperature will plummet and today it dropped to 20 degrees before the burner fired. Why is that?"

you say that if you turn off zone 1 the flow temp etc rises to 71C:
Are you saying that zone 1 has been on, on its own? and if so and the temperature remains at 71 deg for some time then that suggests to me that there is or should be some pump overrun but because the ABV is presently shut then there is no heat dissipation as the boiler internal by pass is only a few inches long and won't dissipate any heat?. Can you hear/detect any pump or maybe fan noise after switching off Zone 1?.

you then say " If I immediately turn on Zone 2 (from cold) the boiler will immediately go into a 204 and then a 202. "
Are you saying here that the boiler is still displaying the 71C when you turn on Zone 2.because if you are then it will go into a 204/202 and if Zone 2 is stone cold then it will obviously fall to 20C or whatever because you are now just circulating Zone 2 (cold) water initially, Zone 1 is "gone".

I would ask WB if they do employ pump overrun and I would then set the ABV to o.25 if they do.

powerade

Your interpretation is 100% spot on. When the heating turns off I can hear the boiler, probably for a couple of minutes after the burner has switched off, followed by a click.
You say that Zone 1 water is gone and you are circulating zone 2 water. So, presumably Zone 2 water returns to the boiler when the Zone is turned on and heats up as it circulates. Hence the reason why it will initially be very cold?

I reset the ABV today to 0.25 btw.

John.G

Some boilers just run the fan only for a few minutes or so to dissipate the heat out through the flue so it that case the ABV will achieve nothing on all zones shutdown if no pump overrun.

Yes re Zone 2 circulation, you have 4 rads full of water at say 20C and the pipework and heat exchanger full of hot water at 65/70C but these will only contain 4 or 5 litres of water whereas the vast majority of the water in the rads, maybe 30 litres will determine that the initial temp is probably only 23C or so, the temp rise through the boiler is then solely determined by the boiler output and the circulation flow rate, so assuming a boiler output of 24 kw and a flowrate of say 15 LPM will result in a deltaT across the boiler of 23C resulting in a flow temperature of 46C but then the return temperature will start rising and even though the deltaT remains the same the flow temperature will rise very rapidly to its set point at which time the boiler will modulate down. Thats why boilers when firing up from cold in the morning may take 20 minutes or so as not only are they meeting the heat demand but are also heating maybe 75/100 litres of water from 20C to 65C or whatever.

powerade

This is the response from WB re boiler behaviour when all of the radiators shut down:

In the event that all of the radiators have shut down this would, by implication, mean that the rooms are up to temperature and there would, therefore, be no demand for heat.

The boiler would overrun its pump to disperse any heat in it via the bypass and any radiator that does not have a TRV fitted.

In this instance the boiler have a status of 203 - System standby.

John.G

That's a excellent response, a bit strange though that I (you?) didn't see any mention of this in the installation printed/e manuals, in your case then because all your rads are on one zone or the other, the pipework will have to do the job, be interesting to watch the flow temp if you switched off both zones and see if it reduces but I would think that the most important reduction is after each cycle as ideally IMO the flow temp should be reduced to ~ 55/58C (set point 65C) which will give the boiler the greatest opportunity to modulate to minimum before it hits 70/71C, in other words that its at its minimum output at ~ 65/67C it will the run for the longest period possible until it reaches the burner off temp at 70/71C, the Vokera is controlled so that the burner demand isn't called for until the flow temp IS SP-5C whereas your boiler burner calls when the flow temp falls to its SP?.

powerade

I think it will re-ignite when the temperature is 6 degrees below the set point, setting 2 3C (see photo).
Just to illustrate the difference in heat loss rates, zone 1 temperature dropped by 9 degrees over 10 hours, Zone 2 dropped by 3.4 degrees in the same period. I have to get Zone 2 up to temperature today so I have both zones on together, both set to 18 degrees. Zone 1 reached temperature at 9:36 so I am now watching the boiler to see how long it takes for the temperature to start rising above 65 degrees. If I time the length of a cycle from the beginning of a 204 to the beginning of the 202, that, in theory, should give me a good indication of the time that I should set for the anti rapid cycle as 3 minutes is clearly not long enough. I also want to see what happens if I change the pump head setting to 3 and adjust the ABV accordingly.
I had a go at measuring the flow and return temps with my Magnusson Infra red gun but it bounces all over the place when I use it on a pipe ( fine on a relatively solid surface).

John.G

My view on 2.3C is that, for example that you set the anti cycle time to something silly like 20 minutes then once the SP-flow temp hits -6C (your setting) then the anti cycle time is aborted and the burner fires up so if I have interpreted it correctly, even a 10 min anti cycle time shouldn't matter as the -6C "wins"?.So the 3 min time is probably calling in the burner before -6C differential.

powerade

I was starting to think that maybe the issue had resolved itself as the boiler had been happily purring along at 65 degrees for quite a while after Zone 1 had turned off. However, I realised that it was still on the evening setting of 22 degrees and, therefore, both zones were still running. As soon as I reset the Zone 1 thermostat to 18 degrees, the boiler temperature rose to 68 degrees, the pressure increased and I could hear the boiler modulating down. 6 minutes later it started a cycle.
Today it dipped into a third 204 which I have seen happen before. This might be due to the fact that I have put the TRV heads back on all of the radiators (except the ones in the thermostat rooms) and turned the TRV on the bedroom rad down to 2. So , I turned the TRV back up to 5 and the flow temperature dropped almost immediately to 60 degrees. When the boiler cycled it brought the temperature back down in two cycles rather than three.
So, if I try to work through the logic of what is happening here, the greater the deficit between the minimum boiler output and the combined radiator output, the longer it takes for the temoetsture to cool down, I.e it takes three anti cycles with three radiators on and two anti cycles with four radiators on.My gut is saying that the ABV has something to do with this. If one radiator has shut down, will the ABV allow more water to flow though the bypass pipe in order to maintain the minimum flow rate. Hence the reason why the water will be slower to cool down as more hot water is being pumped directky back to the boiler when the burner re-ignites. It might also help to explain why the temperature initially rises to 68 degrees when the burner re-ignites after a cycle and then settles back down again to around 63/64 degrees.
I have attached a copy of the biworld ABV data sheet which has the chart you were after John.

powerade

John.G wrote: »

My view on 2.3C is that, for example that you set the anti cycle time to something silly like 20 minutes then once the SP-flow temp hits -6C (your setting) then the anti cycle time is aborted and the burner fires up so if I have interpreted it correctly, even a 10 min anti cycle time shouldn't matter as the -6C "wins"?.So the 3 min time is probably calling in the burner before -6C differential.

I think that the anti cycle time is fixed. So, if the boiler has cooled sufficiently but the full anti cycle period had not elapsed, it will enter a 202 status. So, if the boiler cools off sufficiently in one minute, the status will change to 202 and it will stay at that for two minutes, I.e. three minutes in total

John.G

I don't quite see it that way, why not set the anti cycle time to 10/15 minutes now and see does the boiler burner refire when the differential reaches -6C although what you are saying does sound logical too.

Found this in one of my archives, but refers to some other boiler make.

Anti-cycling time
(This function is also applicable to all other CH modes) When the boiler is switched OFF because the supply temperature reaches CH_Set-point + CH_Hysterese_Up, the controller will wait a period of time (Anti_Cycle_Period →180 sec. settable) before it is allowed to be switched ON again.
This function is to prevent short cycling ON and OFF of the boiler. However, when during the anti-cycle wait time the differential between setpoint and supply temperature gets greater than Anti_Cycle_T_Diff, anti-cycle will be aborted, and the boiler is allowed to start.

powerade

I see what you mean and I had a completely different answer from WB today. I had to get Zone 2 warmed up today and I also had to get back to lowering some radiators and turning off others as I have been running everything on full blast for the last few weeks and it is costing me a fortune. So, at 8am I turned the TRV on the radiator in one of the bedrooms in Zone 2 to a setting of 2. I then turned both Zones on with Zone 1 set at 18 degrees and Zone 2 set at 22 degrees. By 9:36 am Zone 1 was up to a temperature (a rise of 5 degrees) and Zone 2 was up to 16.6 degrees (a rise of 2.4 degrees). Then of course Zone 2 was largely running on its own at this stage, or so I thought, until I realised that it was still on the evening setting, which I mentioed earlier. When I switched zone 1 to the daytime setting, Zone 2 was cycling was all over the place. It finally reached 22 degrees at 4pm today ( 5.4 degrees in 6 1/2 hours). When I set Zone 1 to the evening temperature of 22 degrees, I also turned the TRVs down to a setting of 3 on the kitchen and hall radiators. Zone 1 was then cycling, not as badly as Zone 2 but enough to slow things down. I tested with the pump speed at 0, 2 & 3 but it made no difference. I called the plumber but he had clue. So, I've had enough of trying to figure this out. There appears to be either a fundamental problem with my particular boiler or with the design in general as it cannot efficiently manage the heat demand in any zone if it is below a certain KW value. What that value is I do not know but I have passed this back to Worcester Bosch. I can accept that a degree of cycling is normal and sometimes necessary but I think that this boiler is not suited to a zoned system as the flow gets to hot too quickly and it takes too long to cool down.

John.G

Well, its not for want of effort on your part that you still have problems.

I still wouldn't be too happy with that ABV which I presume was installed with the zoning as, despite what Biworld say should IMO be drop tight with a setting of anything > 0.35, you said in post 53 that it was at a setting of 0.1 and the system was still "working" but short of removing it and testing it then you will never know, but, overall, it is hard to avoid the conclusion that this boiler has to be in modulating mode at all times.

powerade

No, it's certainly not for the want of trying and thank you again for all of your input. I totally agree with you with regard to the ABV and I'm not done yet. I discovered today that when you set the pump speed to zero, you get two new boiler menu items to set a minimum and maximum pump speed. I also found a WB technical info sheet on these two settings which I have attached to this post. It cost me 10 euro to run my heating today which is a joke, considering the investment that I have already made into a combi boiler and heating zones. I will put pressure on WB to figure this out but I will also continue to educate myself in the workings of this system as there is logic there somewhere. I just need to find it.

powerade

Attachment.

John.G

I would suggest that the very first chance you get (system drained or whatever) replace that ABV with a manual gate valve (even temporarily) as you are running the pump in constant pressure mode and it is very easy to set the valve to give whatever by pass you require, if any.

John.G

powerade wrote: »

Attachment.

Setting 5 in the normal menu for pump control runs the pump based on boiler output but overall, I reckon setting 4 (3M, constant head) is the best available option.

And, if only for interest, have you tried increasing the cycle time from 3 min to say 10 min?.

powerade

I can't see a setting 5 for the pump head speed, only 0 to 4? I changed the anti cycle time to 20 minutees and and that is what it took. I have now changed it to 5 minutes. I am leaving Zone 2 to run all day @ 22 degrees. It is relatively mild today and it is up to 21 degrees right now so it should be there in an hour or so. I will also run Zone 1 as normal as I want to get a feel for my energy consumption. In the meantime I can keep an eye on the anti cycling and, more importantly, get some proper assistance from WB. Noted re ABV 👍👍

John.G

2.1E - Pump switch mode setting ▶ Selectable values for pump head. – 4 = Pump energy save on – 5 = Depends on heat request.

powerade

I didn't touch that setting so it is still at no 4. I deliberately avoided bringing the hot water into this discussion but I can't avoid it any longer. This morning I had a d4 error code (flow temperature is rising too fast). All of the taps are mixers in Zone 2 and people always seem to leave them partly turned towards hot. The tap is turned on for a nano second but the system goes I nbto a 201 status followed by a 305. Then when the CH needs to fire up again, the measured temperature is too high and we get a 204/202. If there are subsequent short demands for HW in rapid succession the sysyen cannot cope and we get HW and CH cycles that finally end with a d4. What I really can't understand is how running the hot water can have any effect on the CH flow temperature. When the HW is turned off, for example, you can see the flow temperature shoot up to 75 degrees. I need to observe this a bit more but this can't be right. The heating demand is satisfied in both zones at the moment and the hot water has not been turned on in a while but the system has been running HW rapid anti cycles (status code 305) roughly every 10 minutes for the last half hour &#55358;&#56596;&#55358;&#56596;&#55358;&#56596;

John.G

Pump issue maybe?? despite being renewed. Only suggest now is switch off all power to boiler for a minute or so then power up and restore default setting.
Other possibility is that the boiler heat exchanger is blocked/partially blocked or diverter valve.

powerade

WB are sending an engineer out.